1. Technical Field
This invention relates to material handling systems and, more particularly, to building pallets using robotic systems.
2. Description of the Related Art
Material handling systems are used in a wide variety of environments to receive, store, and load cases of goods for delivery to customers. Generally, material handling systems include a data processor which can examine received customer orders to determine how many cases of customer selected product are to be included on a pallet for delivery to the customer.
Typically, full layer gantries and palletizers are utilized to build pallets having full layers of cases. A full layer of cases refers to a layer having a “footprint” or perimeter which approximates the perimeter of the pallet base, and thus, is substantially square or rectangular in shape. For example, full layer gantries can pull entire layers of cases from a supply pallet having a single product and transfer the entire layer to a pallet being built for delivery to a customer. The palletizer can form full layers of identical cases or cases that are substantially similar in height, width, and length, despite the fact that the cases are not identical in terms of content.
Cases which cannot be readily grouped into full pallet layers, particularly those cases which are not substantially similar in height, width, and/or length, are loaded onto the pallet one by one either by hand or using robots. Presently available pallet configuration systems designed for use with robots, however, often are unable to design or configure stable pallets. Rather, conventional pallet configuration systems attempt to maximize the usable volume of a pallet. Such systems allocate a predetermined volume to each pallet based upon the length and width of the pallet base that will be used to construct the physical pallet as well as the allowable height of a pallet as determined from the loading bay of a transport vehicle, the pallet height that can be accommodated by the automated material handling system, and/or other safety and equipment concerns.
To maximize pallet volume; conventional pallet configuration systems which work cooperatively with robots tend to abandon the concept of adding layers of cases to a pallet in favor of a columnar approach. That is, such systems typically add cases to pallets by stacking additional cases directly atop of cases already placed on the pallet. This technique results in pallets made up of a series of columns rather than layers of interlocking cases. Pallets built with columns of cases, however, can be unstable and subject to collapse. In fact, pallet instability often increases with column height. This stands in contrast to more secure methods of arranging cases using interlocking layers which resemble the layers of bricks within a masonry wall.
While volume usage may or may not be maximized using a columnar approach, the disregard for pallet stability can lead to significant problems with respect to safety and material handling system efficiency. Specifically, a finished pallet still must be transported to a stretch wrapper or other means of securing the cases on the pallet before the pallet can be loaded onto a transport vehicle. While in transit within the material handling system between the robot and the securing station, an unstable pallet can topple over. Such mishaps lead to significant increases with respect to product delivery time and cost. In particular, for each pallet that topples over or loses cases, the pallet building equipment may have to be stopped, the toppled pallet and/or cases must be cleared from the equipment line and rebuilt, and the pallet building equipment must be restarted. More importantly, when an unstable pallet topples over, the safety of those nearby is jeopardized.